This invention relates to the art of apparatus for performing operations such as cutting sheet material like cloth, and more particularly to a new and improved pin for use in apparatus for supporting and matching sheet material during such operations.
One area of use of the present invention is supporting or matching patterned sheet material in a stack for cutting a pattern from the stack, although the principles of the present invention can be variously applied. The matching of plaids, stripes, checked fabrics has been an expensive and difficult manual process for apparel manufacturers with stringent quality matching requirements. Problems can occur because the panels making up a garment must be correctly matched, and the pattern of each panel must be in the correct position in order for the whole garment to match perfectly. Furthermore, distortion in the fabric sometimes causes the size of the check or pattern to differ and stripes are not always straight.
One proposed solution to the foregoing is known in the art as a pin table having a supporting surface provided with a plurality of apertures therethrough arranged in closely spaced relation in a grid-like pattern on the supporting surface. The table includes holding and supporting means for receiving a plurality of pins at the ends opposite the sharp ends thereof and holding the pins substantially perpendicular to the supporting surface and locating the heads in registry with the apertures. In use, a pattern is placed on the supporting surface provided with the plurality of pins extending through apertures, the pins are lowered so that the heads are below the surface for removal of the pattern whereupon sheet material is placed so the surface, typically a plurality of plies being laid up in a stack, and simultaneously the pins are raised and moved through the sheet material to maintain alignment and matching of the plies in the stack. The pattern then is placed on the sheet material in a position determined by the location of the pins, the pins are lowered and the material is shaped such as by cutting.
One problem encountered with apparatus of the foregoing type is that a large stack of tightly woven fabric material can tend to grab or lock onto the pins extending therethrough as the apparatus operates to lower the pins as described hereinabove. Such grabbing or locking action by the fabric material can tend to pull the pins out of the holding and supporting apparatus thereby interfering with normal operation and resulting in unwanted delay in re-installing the pins.
Some pin tables of the foregoing type also include an arrangement for developing a positive pressure to apply a flotation force to sheet material on the surface to facilitate movement of the material along the surface. In particular, there is provided a manifold arrangement connected to a source of positive pressure, a plurality of openings in the supporting surface, a fluid sealing component for sealing the apertures while allowing pins to be moved therethrough, and conduits for connecting the manifold to the openings to supply positive pressure to the openings for applying a flotation force to sheet material on the surface. An example of the fluid sealing component is a sheet of rubber or like material extending along the lower and inner surface of the supporting surface in a manner blocking or covering the apertures to prevent fluid flow through the apertures. An important consideration in the foregoing arrangement is that during set-up when the pins are inserted in the apparatus by the operator, the pins do not punch permanent holes in the sheet of sealing material.
Thus, it would be highly desirable to provide a pin for the foregoing apparatus which is positively held in the holding and supporting means in a manner preventing unwanted withdrawal yet will not damage fluid sealing material associated with the pin receiving apertures in forms of the apparatus having flotation force capability. In addition, it would be highly desirable to provide such a pin which is sufficiently strong to resist bending when fabric or stacks thereof are pulled or otherwise moved along the table surface, and also to provide such a pin which facilitates fabric movement thereon.